One of the most important issues in animal management is to determine the optimal captive environment for the physical and psychological well-being of a particular species. Estimates of well-being require data on behavior, physiology, trauma, health, and reproduction of animals under different living conditions. The present project seeks to provide this information for species such as the chimpanzee (Pan troglodytes), rhesus macaque (Macaca mulatta), and pigtail macaque (M. nemestrina). Data collected on these three species under a variety of conditions with standardized protocols will provide a computerized data base that will enhance the ability of national breeding programs to justify existing housing conditions and/or provide an empirical basis for the design of future facilities. The project is also part of an ongoing effort to develop a new theoretical model of environmental effects on aggressive behavior. Nonhuman primates have many checks on aggression, and appear to effectively cope with social tension related to crowding through appeasement and peacemaking. In 1997, data were collected on a group of chimpanzee housed in a large naturalistic enclosure at Busch Gardens, Florida. Data collection consisted of behavioral observations and fecal samples, following the same methodology that we used the previous years for the groups living at the Yerkes Primate Center. The fecal samples are used to assess level of stress hormones such as cortisol (an article on the validation of the method was published in early 1998). Comparisons of the data collected on groups housed under different conditions at the Yerkes Center suggest that chimpanzee behavior differs depending on the density condition and the number of neighboring groups housed nearby. In addition, data on wounds recorded every week for each chimpanzee living at the Yerkes Center show that housing condition affects the frequency and severity of the wounds. A NATO Collaborative Research Grant has supported an extension of our project to the large group of chimpanzees of the Arnhem zoo in whic h similar data have been collected. Behavioral observations have also been done on two groups of pigtail macaques housed in small enclosures at the New Iberia Primate Center, Louisiana. These data will be compared with data already collected on groups of the same species housed in larger compounds at the Yerkes Center. Observations have also been completed on one of the Yerkes groups after it was moved into a larger compound to document behavioral changes. A first study on the short-term effects of increased density in a sample of 45 chimpanzees was published we found that under high-density conditions social behavior was reduced, whereas behavioral indicators of stress increased. Another published article dealt with an empirical test of behavioral indicators of stress and anxiety in chimpanzees. Video images of chimpanzees, pigtail and rhesus macaques collected and catalogued in previous years have been assembled into videotapes that will support a behavior manual. Videotapes and the behavior manual will be resources to assist others in the interpretation of the computerized data base.